The SMX2200 and SMX3000 series of Smart-UPS use Smart external battery backs to increase runtime. Each battery pack contains a temperature probe to assist the UPS with Temperature compensated charging.
If you connect external batteries, but fail to connect the internal battery that is built into the UPS, the UPS will misinterpret this as an issue with the Battery Temperature Sensor.
Fault modes reported may include "a fault exists at the battery temperature sensor", or "Warning State: Batt Temp Sensor". The battery temperature may show a reading of 59 Degrees Celsius.

Resolution:

To correct this, please ensure the internal battery of the UPS is connected correctly. Please refer to the installation guide that accompanies the UPS or installation instructions from our website.